Hello Rick, 

This is correct for the RoyalLightTheme. Only the Default, IgTheme and Office 2010 Blue Themes have this layout style for the expansion indicators. So you will have to take a look at those styles and import them/replace what RoyalLight is doing. 

I think I am nearly there. If I can understand this last thing I believe I can finish....

My problem is this: The RoyalLight theme using > and a down pointing version of > for the collapsed and expanded indicators in the XamTreeGrid. I have managed to get all the colors, cell borders, etc that I want to change implemented but I cannot figure out where these graphics are coming from. It would seem that the areas in DataPresenterRoyalLight_Express starting around line 4721 would be the target area. Specifically starting at line 4788 ****ExpandCollapseToggle Style*** this code would seem to imply the style:

   <!--  ********************************** ExpandCollapseToggle Style **********************************  -->
    <Style x:Key="ExpandCollapseToggleStyle" TargetType="{x:Type  ToggleButton}">
        <Setter Property="Focusable" Value="False" />
        <Setter Property="Width" Value="22" />
        <Setter Property="Height" Value="22" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type ToggleButton}">
                    <Border Background="{StaticResource TransparentBrush}" Padding="0">
                        <Grid>
                            <Path x:Name="ExpansionIndicatorCollapsed"
                                  Width="5"
                                  Height="8"
                                  HorizontalAlignment="Center"
                                  VerticalAlignment="Center"
                                  Data="M60,40L60,20 70,30z"
                                  Fill="{StaticResource ExpansionIndicatorGlyphBackgroundBrush}"
                                  RenderTransformOrigin="0.5,0.5"
                                  Stretch="Fill"
                                  Stroke="{StaticResource ExpansionIndicatorGlyphBorderBrush}"
                                  StrokeThickness="1"
                                  UseLayoutRounding="False" />
                            <Path x:Name="ExpansionIndicatorExpanded"
                                  Width="6"
                                  Height="6"
                                  HorizontalAlignment="Center"
                                  VerticalAlignment="Center"
                                  Data="M0.5,6.4997156 L3.3283137,3.6714226 3.6714667,3.6714429 3.6714465,3.3282926 6.4997594,0.50000001 6.500113,6.5000692 z"
                                  Fill="{StaticResource ExpansionIndicatorGlyphExpandedBackgroundBrush}"
                                  RenderTransformOrigin="0.5,0.5"
                                  Stretch="Fill"
                                  Stroke="{StaticResource ExpansionIndicatorGlyphBorderBrush}"
                                  StrokeThickness="1"
                                  UseLayoutRounding="False"
                                  Visibility="Collapsed" />
                        </Grid>
                    </Border>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter TargetName="ExpansionIndicatorCollapsed" Property="Stroke" Value="{StaticResource ExpansionIndicatorGlyphHoverBackgroundBrush}" />
                            <Setter TargetName="ExpansionIndicatorCollapsed" Property="Fill" Value="{StaticResource ExpansionIndicatorGlyphHoverBackgroundBrush}" />
                            <Setter TargetName="ExpansionIndicatorExpanded" Property="Stroke" Value="{StaticResource ExpansionIndicatorGlyphHoverBackgroundBrush}" />
                            <Setter TargetName="ExpansionIndicatorExpanded" Property="Fill" Value="{StaticResource ExpansionIndicatorGlyphHoverBackgroundBrush}" />
                        </Trigger>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter TargetName="ExpansionIndicatorExpanded" Property="Visibility" Value="Visible" />
                            <Setter TargetName="ExpansionIndicatorCollapsed" Property="Visibility" Value="Collapsed" />
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

Alas no amount of fiddling affects my outcome

I get this

but I want this

That is as far as the > versus + is concerned. 

I am looking in the wrong place undoubtedly. But I have worked the entire DataPresenter chain for the RoyalLight theme so I am at a loss.

If I could crack this nut my up coming demo would be perfect.

Thx

Rick

Michael thank you for the themes zip file. A lot of my problems are in the xaml contained in the DefaultStyles folder. Could I get the Default files folder that is used to build the 18.2 release. The files in the 18.2 distribution are not current. Please see above

Thx, Rick